The Ring programming language version 1.4.1 book - Part 14 of 31

Ring Documentation, Release 1.4.1
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48.6. Using Threads 368

CHAPTER
FORTYNINE
USING RINGLIBSDL
In this chapter we will learn about using RingLibSDL to create games based on the LibSDL, SDLImage, SDLTTF and
SDLMixer libraries.
Tip: RingLibSDL is not distributed with the binary releases for desktop which uses RingAllegro
Note: To use RingLibSDL, Check ring/android/ringlibsdl folder.
49.1 Create Window
Example:
Load "libsdl.ring"
SDL_Init(SDL_INIT_EVERYTHING)
win = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN)
SDL_Delay(2000)
SDL_DestroyWindow(win)
SDL_Quit()
49.2 Display Image
Example:
Load "libsdl.ring"
ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC )
bmp = SDL_LoadBMP("hello.bmp")
tex = SDL_CreateTextureFromSurface(ren,bmp)
SDL_FreeSurface(bmp)
SDL_RenderClear(ren)
SDL_RenderCopy2(ren,tex)
SDL_RenderPresent(ren)
SDL_Delay(2000)
SDL_DestroyTexture(tex)
SDL_DestroyRenderer(ren)
SDL_Quit()
369

49.3 Switch between two images
Example:
Load "libsdl.ring"
bmp = SDL_LoadBMP("hello.bmp")
bmp = SDL_LoadBMP("hello2.bmp")
tex2 = SDL_CreateTextureFromSurface(ren,bmp)
for x = 1 to 10 showtex(tex) showtex(tex2) next
SDL_DestroyTexture(tex2)
SDL_Quit()
func showtex oTex
SDL_RenderCopy2(ren,oTex)
SDL_Delay(200)
49.4 Draw Rectangle
Example:
Load "libsdl.ring"
rect = sdl_new_sdl_rect()
sdl_set_sdl_rect_x(rect,10)
sdl_set_sdl_rect_y(rect,10)
sdl_set_sdl_rect_w(rect,100)
sdl_set_sdl_rect_h(rect,100)
SDL_SetRenderDrawColor(ren,255,255,255,255)
SDL_RenderDrawRect(ren,rect)
sdl_destroy_sdl_rect(rect)
SDL_Delay(2000)
SDL_Quit()
49.3. Switch between two images 370

49.5 Display PNG Images
Example:
Load "libsdl.ring"
bmp = IMG_Load("hello3.png")
SDL_RenderCopy2(ren,tex)
SDL_Delay(2000)
SDL_Quit()
49.6 Use TTF Fonts
Example:
Load "libsdl.ring"
TTF_Init()
font = TTF_OpenFont("pirulen.ttf", 16)
color = sdl_new_sdl_color()
sdl_set_sdl_color_r(color,0)
sdl_set_sdl_color_g(color,255)
sdl_set_sdl_color_b(color,0)
text = TTF_RenderText_Solid(font,"Welcome to the Ring language",color)
surface = SDL_GetWindowSurface(win)
SDL_BlitSurface(text, nullpointer(), surface, nullpointer())
SDL_UpdateWindowSurface(win)
SDL_Delay(2000)
SDL_Destroy_SDL_Color(color)
SDL_FreeSurface(text)
TTF_CloseFont(font)
SDL_Quit()
49.7 Display Transparent Images
Example:
49.5. Display PNG Images 371

Load "libsdl.ring"
flags = IMG_INIT_JPG | IMG_INIT_PNG
IMG_Init(flags)
bmp = IMG_Load("stars.jpg")
SDL_RenderCopy(ren,tex,nullpointer(),nullpointer())
bmp = IMG_Load("player.png")
# Image - Set Transparent color (white)
myformat = sdl_get_sdl_surface_format(bmp)
white = SDL_MapRGB(myformat, 255, 255, 255)
SDL_SetColorKey(bmp, SDL_True, white)
rect = sdl_new_sdl_rect()
SDL_RenderCopy(ren,tex,nullpointer(),rect)
SDL_SetTextureBlendMode(tex,2)
SDL_SetTextureAlphaMod(tex,255)
SDL_RenderCopy(ren,tex,nullpointer(),rect)
SDL_Destroy_SDL_Rect(rect)
SDL_Delay(2000)
SDL_Quit()
49.8 Close Window Event
Example:
Load "libsdl.ring"
49.8. Close Window Event 372

myevent = sdl_new_sdl_event()
while true
thevent = sdl_pollevent(myevent)
switch sdl_get_sdl_event_type(myevent)
on sdl_get_sdl_quit()
exit
on sdl_get_sdl_keydown()
Key = SDL_GET_SDL_Event_key_keysym_sym(myevent)
if key = 27 exit ok
off
end
SDL_Quit()
49.9 Mouse Events
Example:
Load "libsdl.ring"
win = SDL_CreateWindow("Mouse Events ", 100, 100, 640, 480, SDL_WINDOW_SHOWN)
TTF_Init()
font = TTF_OpenFont("pirulen.ttf", 16)
color = sdl_new_sdl_color()
sdl_set_sdl_color_r(color,0)
sdl_set_sdl_color_g(color,255)
sdl_set_sdl_color_b(color,0)
surface = SDL_GetWindowSurface(win)
while true
cMsg = ""
sdl_pollevent(myevent)
on SDL_QUIT
exit
on SDL_KEYDOWN
if key = 27 exit ok
on SDL_MOUSEBUTTONDOWN
if sdl_get_Sdl_Event_button_button(myevent) = SDL_BUTTON_LEFT
SDL_SETWINDOWTITLE(win, " Button_Left_Down " )
but sdl_get_Sdl_Event_button_button(myevent) = SDL_BUTTON_MIDDLE
SDL_SETWINDOWTITLE(win, " Button_Middle_Down " )
but sdl_get_Sdl_Event_button_button(myevent) = SDL_BUTTON_RIGHT
SDL_SETWINDOWTITLE(win, " Button_Right_Down " )
ok
on SDL_MOUSEMOTION
49.9. Mouse Events 373

sdl_fillrect(surface,nullpointer(),0)
if sdl_get_sdl_event_motion_xrel(myevent) < 0
cMsg += " Left "
else
cMsg += " Right "
ok
if sdl_get_sdl_event_motion_yrel(myevent) < 0
cMsg += " Up "
else
cMsg += " Down "
ok
cMsg += " x = " + sdl_get_sdl_event_motion_x(myevent)
cMsg += " y = " + sdl_get_sdl_event_motion_y(myevent)
showmsg(cMsg)
off
end
SDL_Destroy_SDL_Color(Color)
TTF_CloseFont(font)
SDL_Quit()
func showmsg mymsg
text = TTF_RenderText_Solid(font,mymsg,color)
SDL_BlitSurface(text, nullpointer(), surface, nullpointer())
SDL_UpdateWindowSurface(win)
SDL_FreeSurface(text)
49.10 Play Sound
Example:
Load "libsdl.ring"
Mix_OpenAudio( 44100, MIX_DEFAULT_FORMAT , 2, 10000)
Mix_AllocateChannels(4)
sound = Mix_LoadWav( "sound.wav" )
Mix_VolumeChunk(sound,1)
Mix_PlayChannel(1,sound,0)
while true
thevent = sdl_pollevent(myevent)
on sdl_get_sdl_quit()
exit
on sdl_get_sdl_keydown()
if key = 27 exit ok
off
end
Mix_FreeChunk( sound )
Mix_CloseAudio()
49.10. Play Sound 374

Mix_Quit()
SDL_Quit()
49.10. Play Sound 375

CHAPTER
FIFTY
DEMO PROJECT - GAME ENGINE FOR 2D GAMES
In this chapter we will learn about using the different programming paradigms in the same project.
We will create a simple Game Engine for 2D Games.
You can use the Engine directly to create 2D Games for Desktop or Mobile.
50.1 Project Layers
The project contains the next layers
• Games Layer (Here we will use declarative programming)
• Game Engine Classes (Here we will use the Object-Oriented Programming paradigm)
• Interface to graphics library (Here we will use procedural programming)
• Graphics Library bindings (Here we have RingAllegro and RingLibSDL)
50.2 Graphics Library bindings
We already have RingAllegro to use the Allegro game programming library and we have RingLibSDL to use the
LibSDL game programming library.
Both of RingAllegro and RingLibSDL are created using the C language with the help of the Ring code generator for
extensions.
Each of them is over 10,000 lines of C code which is generated after writing simple configuration files (That are
processed by the code generator).
Each configuration file determines the functions names, structures information and constants then the generator process
this configuration file to produce the C code and the library that can be loaded from Ring code.
Using RingAllegro and RingLibSDL is very similar to using Allegro and LibSDL from C code where you have the
same functions but we can build on that using the Ring language features
• RingAllegro Source Code : https://github.com/ring-lang/ring/tree/master/extensions/ringallegro
• RingLibSDL Source Code : https://github.com/ring-lang/ring/tree/master/extensions/ringsdl
376

50.3 Interface to graphics library
In this layer we have gl_allegro.ring and gl_libsdl.ring
Each library provides the same functions to be used with interacting with the Graphics Library.
This layer hides the details and the difference between RingAllegro and RingLibSDL.
You have the same functions, Just use it and you can switch between Allegro and LibSDL at anytime.
Why ?
Allegro is very simple, we can use it to quickly create 2D games for Windows, Linux and MacOS X.
In Ring 1.0 we started by supporting Allegro.
Also LibSDL is very powerful and popular, very easy to use for Mobile Development.
Ring 1.1 comes with support for LibSDL so we can quickly create games for Mobile.
Note: We can use just one library for Desktop and Mobile development.
• gl_allegro.ring source code : https://github.com/ring-lang/ring/blob/master/ringlibs/gameengine/gl_allegro.ring
• gl_libsdl.ring source code : https://github.com/ring-lang/ring/blob/master/ringlibs/gameengine/gl_libsdl.ring
50.4 Game Engine Classes
The Engine comes with the next classes
• GameBase class
• Resources class
• Game class
• GameObject class
• Sprite class
• Text class
• Animate class
• Sound class
• Map class
• Source Code : https://github.com/ring-lang/ring/blob/master/ringlibs/gameengine/gameengine.ring
50.5 Games Layer
In this layer we create our games using the Game Engine classes
The classes are designed to be used through Declarative Programming.
In our games we will use the next classes
• Game class
• Sprite class
50.3. Interface to graphics library 377

• Text class
• Animate class
• Sound class
• Map class
Note: Other classes in the engine are for internal use by the engine.
We will introduce some examples and three simple games :-
• Stars Fighter Game
• Flappy Bird 3000 Game
• Super Man 2016 Game
50.6 Game Class
The next table present the class attributes.
Attributes Description
FPS Number determines how many times the draw() method will be called per second.
FixedFPS Number determines how many times the animate() method will be called per second.
Title String determines the window title of the game.
aObjects List contains all objects in the game
shutdown True/False value to end the game loop
The next table present the class methods.
Method Description
refresh() Delete objects.
settitle(cTitle) Set the window title using a string parameter.
shutdown() Close the application.
The next table present a group of keywords deﬁned by the class.
Keyword Description
sprite Create new Sprite object and add it to the game objects.
text Create new Text object and add it to the game objects.
animate Create new Animate object and add it to the game objects.
sound Create new Sound object and add it to the game objects.
map Create new Map object and add it ot the game objects.
50.7 GameObject Class
50.6. Game Class 378

enabled True/False determine the state of the object (Active/Not Active)
x Number determine the x position of the object.
y Number determine the y position of the object.
width Number determine the width of the object.
height Number determine the height of the object.
nIndex Number determine the index of the object in objects list.
animate True/False to animate the object or not.
move True/False to move the object using the keyboard or not.
Scaled True/False to scale the object image or not.
draw Function to be called when drawing the object.
state Function to be called for object animation.
keypress Function to be called when a key is pressed.
mouse Function to be called when a mouse event happens.
Method Description
keyboard(oGame,nkey) Check Keyboard Events
mouse(oGame,nType,aMouseList) Check Mouse Events
rgb(r,g,b) Return new color using the RGB (Red, Green and Blue) Values.
50.8 Sprite Class
Parent Class : GameObject Class
image String determine the image ﬁle name.
point Number determine the limit of automatic movement of the object.
direction Number determine the direction of movement.
nstep Number determine the increment/decrement during movement.
type Number determine the object type in the game (Optional).
transparent True/False value determine if the image is transparent.
Method Description
Draw(oGame) Draw the object
50.9 Text Class
Parent Class : Sprite Class
size Number determine the font size
font String determine the font ﬁle name
text String determine the text to be displayed
color Number determine the color
50.8. Sprite Class 379

Method Description
50.10 Animate Class
frames Number determine the number of frames
frame Number determine the active frame
framewidth Number determine the frame width.
animate True/False determine using animate or not.
scaled True/False determine scaling image or not.
Method Description
50.11 Sound Class
Parent Class : GameObject Class
file String determine the sound file name.
once True/False determine to play the file one time or not (loop).
Method Description
playsound() Play the sound file
50.12 Map Class
aMap List determine the map content using numbers.
aImages List determine the image used for each number in the map.
BlockWidth Number determine the block width (default = 32).
BlockHeight Number determine the block height (default = 32).
Animate True/False determine the animation status.
Method Description
getvalue(x,y) Return the item value in the Map according to the visible part
50.10. Animate Class 380

50.13 Using the Game Engine - Creating the Game Window
Load "gameengine.ring" # Give Control to the Game Engine
func main # Called by the Game Engine
oGame = New Game # Create the Game Object
{
title = "My First Game"
} # Start the Events Loop
Note: if you want to deﬁne global variables, this must be before load “gameengine.ring” because this instruction will
give the control to the game engine.
Screen Shot:
50.14 Using the Game Engine - Drawing Text
50.13. Using the Game Engine - Creating the Game Window 381

{
text {
x = 10 y=50
animate = false
size = 20
file = "fonts/pirulen.ttf"
text = "game development using ring is very fun!"
color = rgb(0,0,0)
}
Screen Shot:
50.15 Using the Game Engine - Moving Text
50.15. Using the Game Engine - Moving Text 382

{
text {
x = 10 y=50
animate = false
size = 20
color = rgb(0,0,0) # Color = black
}
text {
x = 10 y=150
# Animation Part =====================================
animate = true # Use Animation
direction = GE_DIRECTION_INCVERTICAL # Increase y
point = 400 # Continue until y=400
nStep = 3 # Each time y+= 3
#=====================================================
size = 20
text = "welcome to the real world!"
color = rgb(0,0,255) # Color = Blue
}
Screen Shot:
50.15. Using the Game Engine - Moving Text 383

50.16 Using the Game Engine - Playing Sound
{
text {
x = 10 y=50
animate = false
size = 20
color = rgb(0,0,0) # Color = black
}
text {
x = 10 y=150
# Animation Part ======================================
animate = true # Use Animation
direction = GE_DIRECTION_INCVERTICAL # Increase y
50.16. Using the Game Engine - Playing Sound 384

point = 400 # Continue until y=400
nStep = 3 # Each time y+= 3
#======================================================
size = 20
text = "welcome to the real world!"
color = rgb(0,0,255) # Color = Blue
}
Sound { # Play Sound
file = "sound/music1.wav" # Sound File Name
}
50.17 Using the Game Engine - Animation
{
animate {
file = "images/fire.png"
x = 100
y = 200
framewidth = 40
height = 42
nStep = 3 # Used for delay
transparent = true
state = func oGame,oSelf { # Called by engine each frame
oSelf {
nStep--
if nStep = 0
nStep = 3
if frame < 13 # we have 13 frames in animation
frame++ # move to next frame
else
oGame.remove(oself.nIndex) # remove object
ok
ok
}
}
}
50.17. Using the Game Engine - Animation 385

50.18 Using the Game Engine - Animation and Functions
{
for x = 70 to 700 step 50
for y = 70 to 500 step 50
showfire(oGame,x,y)
next
next
func showfire oGame,nX,nY
oGame {
animate {
file = "images/fire.png"
x = nX
50.18. Using the Game Engine - Animation and Functions 386

y = nY
framewidth = 40
height = 42
nStep = 3 # Used for delay
transparent = true
state = func oGame,oSelf { # Called by engine each frame
oSelf {
nStep--
if nStep = 0
nStep = 3
if frame < 13 # we have 13 frames in animation
frame++ # move to next frame
else
frame=1
ok
ok
}
}
}
}
50.18. Using the Game Engine - Animation and Functions 387

50.19 Using the Game Engine - Sprite - Automatic Movement using
Keyboard
Load "gameengine.ring" # Give control to the game engine
{
sprite
{
type = GE_TYPE_PLAYER # Just for our usage
x=400 y=400 width=100 height=100
file = "images/player.png"
transparent = true
Animate=false
Move=true # we can move it using keyboard arrows
Scaled=true
}
50.19. Using the Game Engine - Sprite - Automatic Movement using Keyboard 388

50.20 Using the Game Engine - Sprite - Keypress event
{
sprite
{
transparent = true
Animate=false
Move=false # Custom Movement
Scaled=true
keypress = func oGame,oSelf,nKey {
oSelf {
Switch nKey
on KEY_LEFT
x -= 10
on KEY_RIGHT
x += 10
on KEY_UP
y -= 10
on KEY_DOWN
y += 10
off
}
}
}
50.21 Using the Game Engine - Sprite - Mouse event
{
sprite
{
transparent = true
Animate=false
Scaled=true
oSelf {
50.20. Using the Game Engine - Sprite - Keypress event 389

Switch nKey
on KEY_LEFT
x -= 10
on KEY_RIGHT
x += 10
on KEY_UP
y -= 10
on KEY_DOWN
y += 10
off
}
}
mouse = func oGame,oSelf,nType,aMouseList {
if nType = GE_MOUSE_UP
oSelf {
x = aMouseList[GE_MOUSE_X]
y = aMouseList[GE_MOUSE_Y]
}
ok
}
}
50.22 Using the Game Engine - Sprite - State event
{
sprite
{
transparent = true
Animate=false
Scaled=true
oSelf {
Switch nKey
on KEY_LEFT
x -= 10
on KEY_RIGHT
x += 10
on KEY_UP
y -= 10
on KEY_DOWN
y += 10
off
}
}
mouse = func oGame,oSelf,nType,aMouseList {
50.22. Using the Game Engine - Sprite - State event 390

oSelf {
x = aMouseList[GE_MOUSE_X]
y = aMouseList[GE_MOUSE_Y]
}
ok
}
state = func oGame,oSelf {
oself {
if x < 0 x = 0 ok
if y < 0 y = 0 ok
if x > ogame.width-width
x= ogame.width - width ok
if y > ogame.height-height
y=ogame.height - height ok
}
}
}
50.23 Using the Game Engine - Animate - Events
{
animate {
file = "images/fbbird.png"
x = 10
y = 10
framewidth = 20
scaled = true
height = 50
width = 50
nStep = 3
transparent = true
oSelf {
# Animation
nStep--
if nStep = 0
nStep = 3
if frame < 3
frame++
else
frame=1
ok
ok
50.23. Using the Game Engine - Animate - Events 391

# Move Down
y += 3
if y > 550 y=550 ok
}
}
keypress = func ogame,oself,nKey {
oself {
if nkey = key_space
y -= 55
if y<=0 y=0 ok
ok
}
}
mouse = func ogame,oself,nType,aMouseList {
cFunc = oself.keypress
call cFunc(oGame,oSelf,Key_Space)
ok
}
}
Screen Shot:
50.23. Using the Game Engine - Animate - Events 392

50.24 Using the Game Engine - Map
{
Map {
blockwidth = 80
blockheight = 80
aMap = [
[0,0,0,0,0,0,0,0,0,1,0,0,0,3,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0],
[0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0],
[0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,2,0,0,0,1,0,0,0],
[0,0,0,0,0,0,0,0,0,1,0,0,0,2,0,0,0,3,0,0,0,1,0,0,0,1,0,0,0],
[0,0,0,0,0,0,0,0,0,3,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,3,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0],
50.24. Using the Game Engine - Map 393

[0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0]
]
aImages = ["images/fbwall.png",
"images/fbwallup.png",
"images/fbwalldown.png"]
oSelf {
x -= 3
if x < - 2100 x = 0 ok
}
}
}
Screen Shot:
50.24. Using the Game Engine - Map 394

50.25 Using the Game Engine - Map Events
{
Map {
blockwidth = 80
blockheight = 80
aMap = [
[0,0,0,0,0,0,0,0,0,1,0,0,0,3,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0],
[0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0],
[0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,2,0,0,0,1,0,0,0],
[0,0,0,0,0,0,0,0,0,1,0,0,0,2,0,0,0,3,0,0,0,1,0,0,0,1,0,0,0],
[0,0,0,0,0,0,0,0,0,3,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,3,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0]
]
aImages = ["images/fbwall.png",
"images/fbwallup.png",
"images/fbwalldown.png"]
oSelf {
x -= 3
if x < - 2100 x = 0 ok
}
}
mouse = func ogame,oself,nType,aMouseList {
oSelf {
mX = aMouseList[GE_MOUSE_X]
mY = aMouseList[GE_MOUSE_Y]
nValue = GetValue(mX,mY)
nRow = GetRow(mX,mY)
nCol = GetCol(mX,mY)
Switch nValue
On 1 aMap[nRow][nCol] = 0
Off
}
ok
}
}
50.25. Using the Game Engine - Map Events 395

Screen Shot:
50.26 Using the Game Engine - Object and Drawing
We can use the Object keyword (deﬁned by the game engine) to create objects from the GameObject class.
Example:
{
Object {
x = 0 y=300 width = 200 height=200
draw = func oGame,oSelf {
oSelf {
for t = 1 to 210
gl_draw_circle(x,y,t,
gl_map_rgb(t*random(255),
t*2,t*3),1)
50.26. Using the Game Engine - Object and Drawing 396

next
}
}
oSelf {
if x <= 800
x+= 3
else
x=0
ok
}
}
oSelf {
Switch nKey
on KEY_LEFT
x -= 10
on KEY_RIGHT
x += 10
on KEY_UP
y -= 10
on KEY_DOWN
y += 10
off
}
}
}
Screen Shot:
50.26. Using the Game Engine - Object and Drawing 397

The Ring programming language version 1.4.1 book - Part 14 of 31

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The Ring programming language version 1.4.1 book - Part 14 of 31